The default directory where all your newly created databases will be stored is {{ic|/var/lib/postgres/data}}. To change this, follow these steps:

The default directory where all your newly created databases will be stored is {{ic|/var/lib/postgres/data}}. To change this, follow these steps:

−

Create the new directory and make the ''postgres'' user its owner:

+

Create the new directory and make the postgres user its owner:

+

# mkdir -p /pathto/pgroot/data

# mkdir -p /pathto/pgroot/data

# chown -R postgres:postgres /pathto/pgroot

# chown -R postgres:postgres /pathto/pgroot

−

Become the ''postgres'' user, and initialize the new cluster:

+

+

Become the postgres user, and initialize the new cluster:

+

[postgres]$ initdb -D /pathto/pgroot/data

[postgres]$ initdb -D /pathto/pgroot/data

−

If enabled, disable {{ic|postgres.service}}. Copy {{ic|/usr/lib/systemd/system/postgresql.service}} to {{ic|/etc/systemd/system/postgresql.service}} and edit it to change the default {{ic|PGROOT}} and {{ic|PIDFile}} paths.

+

+

If enabled, disable {{ic|postgresql.service}}. Copy {{ic|/usr/lib/systemd/system/postgresql.service}} to {{ic|/etc/systemd/system/postgresql.service}} and edit it to change the default {{ic|PGROOT}} and {{ic|PIDFile}} paths.

+

Environment=PGROOT=''/pathto/pgroot/''

Environment=PGROOT=''/pathto/pgroot/''

...

...

Revision as of 09:09, 29 April 2015

PostgreSQL is an open source, community driven, standard compliant object-relational database system.

This document describes how to set up PostgreSQL. It also describes how to configure PostgreSQL to be accessible from a remote client. If you need help setting up the rest of a web stack, see the LAMP page and follow all of the sections except the one related to MySQL.

Installing PostgreSQL

Note: Commands that should be run as the postgres user are prefixed by [postgres]$ in this article. You can change to the postgres user by running su - postgres as root. Alternatively, if you use sudo, run sudo -i -u postgres as a regular user.

Before PostgreSQL can function correctly, the database cluster must be initialized:

If you do not use a nightly build, then run this command (verified on HHVM 3.6.1) to avoid compile errors:

$ git checkout tags/3.6.0

Then build the extension (if you do not need an improved support for Hack language, then remove -DHACK_FRIENDLY=ON):

$ hphpize
$ cmake -DHACK_FRIENDLY=ON .
$ make

Then copy the built extension:

$ sudo cp pgsql.so /etc/hhvm/

Add to /etc/hhvm/server.ini:

extension_dir = /etc/hhvm
hhvm.extensions[pgsql] = pgsql.so

Create your first database/user

Tip: If you create a PostgreSQL user with the same name as your Linux username, it allows you to access the PostgreSQL database shell without having to specify a user to login (which makes it quite convenient).

Become the postgres user. Add a new database user using the createuser command:

[postgres]$ createuser --interactive

Create a new database over which the above user has read/write privileges using the createdb command (execute this command from your login shell if the database user has the same name as your Linux user, otherwise add -U database-username to the following command):

$ createdb myDatabaseName

Familiarize with PostgreSQL

Access the database shell

Become the postgres user. Start the primary database shell, psql, where you can do all your creation of databases/tables, deletion, set permissions, and run raw SQL commands. Use the -d option to connect to the database you created (without specifying a database, psql will try to access a database that matches your username).

[postgres]$ psql -d myDatabaseName

Some helpful commands:

Get help:

=> \help

Connect to a particular database:

=> \c <database>

List all users and their permission levels:

=> \du

Show summary information about all tables in the current database:

=> \dt

Exit/quit the psql shell:

=> \q or CTRL+d

There are of course many more meta-commands, but these should help you get started.

Optional configuration

Configure PostgreSQL to be accessible from remote hosts

The PostgreSQL database server configuration file is postgresql.conf. This file is located in the data directory of the server, typically /var/lib/postgres/data. This folder also houses the other main configuration files, including the pg_hba.conf.

Note: By default, this folder will not be browsable or searchable by a regular user. This is why find and locate are not finding the configuration files.

Edit the file /var/lib/postgres/data/postgresql.conf. In the connections and authentications section, add the listen_addresses line to your needs:

listen_addresses = 'localhost,my_remote_ip_address'

Take a careful look at the other lines.

Host-based authentication is configured in /var/lib/postgres/data/pg_hba.conf. This file controls which hosts are allowed to connect. Note that the defaults allow any local user to connect as any database user, including the database superuser. Add a line like the following:

Change default encoding of new databases to UTF-8

Note: If you ran initdb with -E UTF8 these steps are not required

When creating a new database (e.g. with createdb blog) PostgreSQL actually copies a template database. There are two predefined templates: template0 is vanilla, while template1 is meant as an on-site template changeable by the administrator and is used by default. In order to change the encoding of new database, one of the options is to change on-site template1. To do this, log into PostgresSQL shell (psql) and execute the following:

First, we need to drop template1. Templates cannot be dropped, so we first modify it so it is an ordinary database:

Administration tools

Upgrading PostgreSQL

Quick guide

This is for upgrading from 9.2 to 9.3, and also works from 9.3 to 9.4.

Tip: If you already migrated from 9.2 to 9.3 and you want to migrate to 9.3 to 9.4, change versions before executing commands!
If /var/lib/postgres/data-9.2 already exists and you just copy-paste all commands, pg_upgrade will complain about the wrong version of the database, because you 9.3's database will be stored in /var/lib/postgres/data-9.2/data/

cannot write to log file pg_upgrade_internal.log Failure, exitingMake sure you are in a directory that the "postgres" user has enough rights to write the log file to (/tmp for example). Or use "su - postgres" instead of "sudo -u postgres".

LC_COLLATE error that says that old and new values are differentFigure out what the old locale was, C or en_US.UTF-8 for example, and force it when calling initdb.

sudo -u postgres LC_ALL=C initdb -D /var/lib/postgres/data

There seems to be a postmaster servicing the old cluster.Please shutdown that postmaster and try again.Make sure postgres is not running. If you still get the error then chances are there is an old PID file you need to clear out.

ERROR: could not access file "$libdir/postgis-2.0": No such file or directory Retrieve postgis-2.0.so from postgis package for version postgresql 9.2 () and copy it to /opt/pgsql-9.2/lib (make sure the privileges are right)

Detailed instructions

Note that these instructions could cause data loss. Use at your own risk.

It is recommended to add the following to your /etc/pacman.conf file:

IgnorePkg = postgresql postgresql-libs

This will ensure you do not accidentally upgrade the database to an incompatible version. When an upgrade is available, pacman will notify you that it is skipping the upgrade because of the entry in pacman.conf. Minor version upgrades (e.g., 9.0.3 to 9.0.4) are safe to perform. However, if you do an accidental upgrade to a different major version (e.g., 9.0.X to 9.1.X), you might not be able to access any of your data. Always check the PostgreSQL home page (http://www.postgresql.org/) to be sure of what steps are required for each upgrade. For a bit about why this is the case see the versioning policy.

There are two main ways to upgrade your PostgreSQL database. Read the official documentation for details.

For those wishing to use pg_upgrade, a postgresql-old-upgrade package is available in the repositories that will always run one major version behind the real PostgreSQL package. This can be installed side by side with the new version of PostgreSQL. When you are ready to perform the upgrade, you can do

pacman -Syu postgresql postgresql-libs postgresql-old-upgrade

Note also that the data directory does not change from version to version, so before running pg_upgrade it is necessary to rename your existing data directory and migrate into a new directory. The new database must be initialized, as described near the top of this page.

Manual dump and reload

You could also do something like this (after the upgrade and install of postgresql-old-upgrade) (NB: below is command for postgres8.4 update, you can find similar command in /opt/ for postgres 9.2 update. )

Troubleshooting

Improve performance of small transactions

If you are using PostgresSQL on a local machine for development and it seems slow, you could try turning synchronous_commit off in the configuration. Beware of the caveats, however.

/var/lib/postgres/data/postgresql.conf

synchronous_commit = off

Prevent disk writes when idle

PostgreSQL periodically updates its internal "statistics" file. By default, this file is stored on disk, which prevents disks spinning down on laptops and causes hard drive seek noise. It is simple and safe to relocate this file to a memory-only file system with the following configuration option:

/var/lib/postgres/data/postgresql.conf

stats_temp_directory = '/run/postgresql'

Can't connect to database through pg_connect()

Install php-pgsql and edit the php.ini file uncommenting the lines extension=pdo_pgsql.so and extension=pgsql.so then restart httpd.